In recent years, the number of patients who are suffered from respiratory diseases such as asthma, pulmonary emphysema and chronic bronchitis has a tendency to increase. One of the most effective therapies for these respiratory diseases is an oxygen inhalation therapy, and an oxygen concentration apparatus by which an oxygen concentrated gas is separated directly from the air, or an oxygen cylinder is becoming to be used as an oxygen supply source needed for the therapy. In the case where the oxygen inhalation therapy is done in a hospital or at home, an oxygen-enriched air supplying apparatus of a pressure variable adsorption type or a membrane type, or that using solid electrolyte membranes which selectively permeates oxygen, or a high-volume fixed-type oxygen cylinder is used.
On the other hand, when a patient goes out for attending a hospital, a portable oxygen cylinder is used. Since it is a cylinder for a respiratory disease patient to carry, the cylinder should be small-sized and light in weight, and high pressure oxygen gas is filled in it so that it can be used for a long time. The potable small-sized oxygen cylinder is provided with a pressure-reducing valve and has a flow controlling function so that oxygen can be supplied to the patient at the flow rate of the prescription.
Further, as a method for extending available time, a respiration-synchronized oxygen-supplying apparatus which has a built-in respiration sensor and an automatic closing valve, and supplies oxygen only during inhalation and not during exhalation of a patient has been proposed by JP-B 3-22185 (JP-B means Japanese examined patent publication), JP-A 59-8972 (JP-A means Japanese unexamined patent publication) or the like.
Further, the respiration-synchronized oxygen-supplying apparatus does not waste oxygen during exhalation, and it is effective also economically, and hence it was proposed to use a respiration-synchronized oxygen-supplying apparatus also in an oxygen concentration apparatus by JP-A 61-131756 or the like. Furthermore, a movable or portable oxygen concentration apparatus which can be driven by a buttery was proposed (see JP-A 7-136271, JP-A 7-136272, JP-A 2000-325482, JP-A 2002-121010 and JP-A 2002-45424), and it is desirable to equip the oxygen concentration apparatus with a respiration-synchronized oxygen-supplying apparatus in order to extend usable time, which is limited by a capacity of the buttery.
In such a respiration-synchronized oxygen-supplying apparatus, the respiration of a user is usually detected by catching nasal respiration with a pressure sensor through a cannula. Consequently, there occurs a case where the respiration is not synchronized when the respiration of a user is weak, or contrarily the respiration rate is abnormally large. There is also a case where it is not synchronized due to the deterioration of the sensor.
Further, in a case where the respiration-synchronized oxygen-supplying apparatus is used together with a portable oxygen concentration apparatus, they are sometimes used even during sleeping, in which the user sometimes breathes through the mouth, and the respiration is not detected by a usual sensor which detects only nasal respiration. In such a case, continuous oxygen supply which is independent to the respiration of the user may be required.
From this point of view, JP-A 2002-143806 proposes a structure in which the first piping system having a solenoid-operated valve and the second piping system having a setting material on which a plurality of orifices are mounted, and when the first piping system or the second piping system are selected by a switching valve, respiration synchronized oxygen supply or continuous oxygen supply can be set in oxygen flow, respectively.